Current cartilage regenerative therapies are not fully effective in treating osteoarthritis of the knee (OAK). We have developed chondrocyte sheets for autologous transplantation and tested these in in vitro and in vivo preclinical studies, and have reported that the transplantation of chondrocyte sheets promoted hyaline cartilage repair in rat, rabbit, and minipig models. However, autologous transplantation of chondrocyte sheets has yet to be reported in humans. Here, we report our combination therapy in which conventional surgical treatment for OAK, is followed by autologous chondrocyte sheet transplantation for cartilage repair. Eight patients with OAK and cartilage defects categorized arthroscopically as Outerbridge grade III or IV receive the therapy. Patients are thoroughly assessed by preoperative and postoperative X-rays, magnetic resonance imaging (MRI), arthroscopy, Knee injury and Osteoarthritis Outcome Score (KOOS), Lysholm Knee Score (LKS), and a laser-induced photoacoustic method to assess cartilage viscoelasticity. Arthroscopic biopsies of all patients are performed 12 months after transplantation for histological evaluation. The properties of the chondrocyte sheets are evaluated using gene expression analysis to investigate the ability to predict the clinical and structural outcomes of the therapy. For this small initial longitudinal series, combination therapy is effective, as assessed by MRI, arthroscopy, viscoelasticity, histology, and the clinical outcomes of KOOS and LKS. Gene marker sets identified in autologous chondrocyte sheets may be predictive of the overall KOOS, LKS, and histological scores after therapy. These predictive gene sets may be potential alternative markers for evaluating OAK treatment.

Human cells and tissue products belong to a relatively new class of medical products. Therefore, limited information is available on the classification and premarket evaluation of human cells and tissue products in the United States (US), the European Union (EU), and Japan. In this study, the definition, legislation, and approval system of these products were surveyed. A total of nine autologous human cells and tissue products approved until October 2013 were collected. The definitions of human cells and tissue products were compatible among the US, the EU and Japan. The products were classified as human cells, tissue, and cellular and tissue-based products (HCT/Ps) in the US, advanced therapy medicinal products (ATMPs) in the EU, and cell/tissue-engineered products in Japan. These products were categorized as biologics and medical device in the US and Japan, and drug in the EU. The issuance of new guidance induced regulatory impact for manufacturer, especially in the US. These products are subjected to the accelerated approval of biological product, the humanitarian device exemption approval, the premarket application approval, the biologics license application approval, and new drug application approval with specific targeting of postapproval registry or surveillance. Of nine autologous human cells and tissue products, four products had been evaluated using clinical experiences or open clinical trials with small subjects, although the rests of products had been evaluated using comparative clinical trials with control treatment. Our survey suggests that autologous human cells and tissue products would need postmarket-oriented evaluation rather than premarket-oriented evaluation for doctors and patients.

Cell sheet transplantation is a key tissue engineering technology. A vascular endothelial growth factor (VEGF)‐releasing fiber mat is developed for the transplantation of multilayered cardiomyocyte sheets. Poly(vinyl alcohol) fiber mats bearing poly(lactic‐co‐glycolic acid) nanoparticles that incorporate VEGF are fabricated using electrospinning and electrospray methods. Six‐layered cardiomyocyte sheets are transplanted with a VEGF‐releasing mat into athymic rats. After two weeks, these sheets produce thicker cardiomyocyte layers compared with controls lacking a VEGF‐releasing mat, and incorporate larger‐diameter blood vessels containing erythrocytes. Thus, local VEGF release near the transplanted cardiomyocytes induces vascularization, which supplies sufficient oxygen and nutrients to prevent necrosis. In contrast, cardiomyocyte sheets without a VEGF‐releasing mat do not survive in vivo, probably undergo necrosis, and are reduced in thickness. Hence, these VEGF‐releasing mats enable the transplantation of multilayered cardiomyocyte sheets in a single procedure, and should expand the potential of cell sheet transplantation for therapeutic applications. image

Osseointegrated implants have been recognized as being very reliable and having long term predictability. However, host-defense mechanisms against infection have been known to be impaired around a dental implant because of the lack of a periodontal ligament (PDL). The purpose of our experimental design was to produce cementum and PDL on the implant surface adopting cell sheet technology. To this aim we used PDL-derived cells, which contain multi-potential stem cells, as the cell source and we cultured them on an implant material constituted of commercially pure titanium treated with acid etching, blasting, and a calcium phosphate (CaP) coating to improve cell attachment. Implants with adhered human PDL cell sheets were transplanted into bone defects in athymic rat femurs as a xenogeneic model. Implants with adhered canine PDL-derived cell sheets were transplanted into canine mandibular bone as an autologous model. We confirmed that PDL-derived cells cultured with osteoinductive medium had the ability to induce cementum formation. The attachment of PDL cells onto the titanium surface with 3 surface treatments was accelerated, compared with that onto the smooth titanium surface, at 40 minutes after starting incubation. Results in the rat model showed that cementum-like and PDL-like tissue was partly observed on the titanium surface with 3 surface treatments in combination with adherent PDL-derived cell sheets. On the other hand, osseointegration was observed on almost all areas of the smooth titanium surface that had PDL-derived cell sheets but did not have the 3 surface treatments. In the canine model, histological observation indicated that formation of cementum-like and PDL-like tissue was induced on the titanium surface with surface treatments and that the PDL-like tissue was perpendicularly oriented between the titanium surface with cementum-like tissue and the bone. Results demonstrate that a periodontal-like structure was formed around a titanium implant, which is similar to the environment existing around a natural tooth. The clinical application of dental implants combined with a cell sheet technique may be feasible as an alternative implant therapy. Furthermore, application of this methodology may play an innovative role in the periodontal, prosthetic, and orthodontic fields in dentistry.

Tissue engineering has become an essential tool in the development of regenerative medicine. We have developed cell sheet–based techniques for use in regenerative medicine that have already been successfully used in clinical applications. Native corneal epithelium is produced from limbal stem cells located in the transition zone between the cornea and the bulbar conjunctiva. Limbal stem cell deficiency (LSCD) is a severe defect of the limbal stem cells leading to vision loss due to conjunctival epithelial invasion and neovascularization. Rabbit LSCD models were treated with transplantable autologous oral mucosal epithelial cell (OEC) sheets fabricated on temperature-responsive cell culture surfaces, after which, the ocular surfaces were clear and smooth with no observable defects. The central part of the reconstructed ocular surface was scraped and wounded, after which proliferating epithelial cells covered the scraped area within a few days. The ocular surfaces were clear and smooth even after repeated scrapings and consisted of only OECs or heterogeneously mixed with corneal epithelial cells. This study demonstrates that transplanted cell sheets containing oral mucosal epithelial stem cells could reconstruct the ocular surface to maintain cornea homeostasis; moreover, they provide an ideal microenvironment to support the proliferation of remaining native limbal stem cells.